TFTs have been widely used in display applications such as liquid crystal displays (LCDs), electronic paper displays (EPDs), and organic light emitting diode displays (OLEDs).
Generally, a TFT structure includes a substrate, a gate electrode, a gate insulator layer, a channel island, a source electrode, and a drain electrode. The gate electrode is disposed on the substrate, the gate insulator layer covers the gate electrode, the channel island is disposed on the gate insulator layer, and the source electrode and the drain electrode are disposed on the channel island.
The above-described type of TFT can be well used in a LCD. However, if the TFT structure is used in an EPD, the channel island might become conductive after being irradiated by external light, which resulting in current leakage occurring in the channel island. As a result of the current leakage, the EPD suffers from abnormal displaying (e.g. image or color distortion).
Therefore, how to avoid abnormal displaying and improve displaying quality of EPDs becomes the area that researchers and developers are focused on.